Evolution of oxygen-ion and proton conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), located near pyrochlore fluorite phase boundary
Autor(a) principal: | |
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Data de Publicação: | 2019 |
Outros Autores: | , , , , , , , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
Texto Completo: | http://hdl.handle.net/20.500.11960/3059 |
Resumo: | Sm2-xCaxZr2O7-x/2 (x = 0, 0.05, 0.1) and Gd2-xCaxZr2O7-x/2 (x = 0.05, 0.1) mixed oxides in a pyrochlore-fluorite morphotropic phase region were prepared via the mechanical activation of oxide mixtures, followed by annealing at 1600 °C. The structure of the solid solutions was studied by X-ray diffraction and refined by the Rietveld method, water content was determined by thermogravimetry (TG), their bulk and grain-boundary conductivity was determined by impedance spectroscopy in dry and wet air (100-900 °C), and their total conductivity was measured as a function of oxygen partial pressure in the temperature range: 700-950 °C. The Sm2-xCaxZr2O7-x/2 (x = 0.05, 0.1) pyrochlore solid solutions, lying near the morphotropic phase boundary, have proton conductivity contribution both in the grain bulk and on grain boundaries below 600 °C, and pure oxygen-ion conductivity above 700 °C. The 500 °C proton conductivity contribution of Sm2-xCaxZr2O7-x/2 (x = 0.05, 0.1) is ~ 1 × 10-4 S/cm. The fluorite-like Gd2-xCaxZr2O7-x/2 (x = 0.1) solid solution has oxygen-ion bulk conductivity in entire temperature range studied, whereas proton transport contributes to its grain-boundary conductivity below 700 °C. As a result, of the morphotropic phase transition from pyrochlore Sm2-xCaxZr2O7-x/2 (x = 0.05, 0.1) to fluorite-like Gd2-xCaxZr2O7-x/2 (x = 0.05, 0.1), the bulk proton conductivity disappears and oxygen-ion conductivity decreases. The loss of bulk proton conductivity of Gd2-xCaxZr2O7-x/2 (x = 0.05, 0.1) can be associated with the fluorite structure formation. It is important to note that the degree of Ca substitution in such solid solutions (Ln2-xCax)Zr2O7-σ (Ln = Sm, Gd) is low, x < 0.1. In both series, grain-boundary conductivity usually exceeds bulk conductivity. The high grain-boundary proton conductivity of Ln2-xCaxZr2O7-x/2 (Ln = Sm, Gd; x = 0.1) is attributable to the formation of an intergranular CaZrO3-based cubic perovskite phase doped with Sm or Gd in Zr sublattice. © 2019 by the authors. |
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Evolution of oxygen-ion and proton conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), located near pyrochlore fluorite phase boundaryPyrochlorePyrochlore–fluorite morphotropic phase regionProton conductivityOxygen—ion conductivityGrain-boundary conductivityThermogravimetryRietveld refinementSm2-xCaxZr2O7-x/2 (x = 0, 0.05, 0.1) and Gd2-xCaxZr2O7-x/2 (x = 0.05, 0.1) mixed oxides in a pyrochlore-fluorite morphotropic phase region were prepared via the mechanical activation of oxide mixtures, followed by annealing at 1600 °C. The structure of the solid solutions was studied by X-ray diffraction and refined by the Rietveld method, water content was determined by thermogravimetry (TG), their bulk and grain-boundary conductivity was determined by impedance spectroscopy in dry and wet air (100-900 °C), and their total conductivity was measured as a function of oxygen partial pressure in the temperature range: 700-950 °C. The Sm2-xCaxZr2O7-x/2 (x = 0.05, 0.1) pyrochlore solid solutions, lying near the morphotropic phase boundary, have proton conductivity contribution both in the grain bulk and on grain boundaries below 600 °C, and pure oxygen-ion conductivity above 700 °C. The 500 °C proton conductivity contribution of Sm2-xCaxZr2O7-x/2 (x = 0.05, 0.1) is ~ 1 × 10-4 S/cm. The fluorite-like Gd2-xCaxZr2O7-x/2 (x = 0.1) solid solution has oxygen-ion bulk conductivity in entire temperature range studied, whereas proton transport contributes to its grain-boundary conductivity below 700 °C. As a result, of the morphotropic phase transition from pyrochlore Sm2-xCaxZr2O7-x/2 (x = 0.05, 0.1) to fluorite-like Gd2-xCaxZr2O7-x/2 (x = 0.05, 0.1), the bulk proton conductivity disappears and oxygen-ion conductivity decreases. The loss of bulk proton conductivity of Gd2-xCaxZr2O7-x/2 (x = 0.05, 0.1) can be associated with the fluorite structure formation. It is important to note that the degree of Ca substitution in such solid solutions (Ln2-xCax)Zr2O7-σ (Ln = Sm, Gd) is low, x < 0.1. In both series, grain-boundary conductivity usually exceeds bulk conductivity. The high grain-boundary proton conductivity of Ln2-xCaxZr2O7-x/2 (Ln = Sm, Gd; x = 0.1) is attributable to the formation of an intergranular CaZrO3-based cubic perovskite phase doped with Sm or Gd in Zr sublattice. © 2019 by the authors.2023-01-02T15:03:04Z2019-08-01T00:00:00Z2019-08-012022-12-05T11:22:39Zinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articleapplication/pdfhttp://hdl.handle.net/20.500.11960/3059eng1996-194410.3390/ma12152452Shlyakhtina, A. V.Abrantes, JoãoGomes, EduardaLyskov, N. V.Konysheva, E. Yu.Chernyak, S. A.Kharitonova, E. P.Karyagina, O. KKolbanev, I. V.Shcherbakova, L. G.info:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2023-06-08T06:45:25Zoai:repositorio.ipvc.pt:20.500.11960/3059Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-19T17:44:43.253924Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse |
dc.title.none.fl_str_mv |
Evolution of oxygen-ion and proton conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), located near pyrochlore fluorite phase boundary |
title |
Evolution of oxygen-ion and proton conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), located near pyrochlore fluorite phase boundary |
spellingShingle |
Evolution of oxygen-ion and proton conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), located near pyrochlore fluorite phase boundary Shlyakhtina, A. V. Pyrochlore Pyrochlore–fluorite morphotropic phase region Proton conductivity Oxygen—ion conductivity Grain-boundary conductivity Thermogravimetry Rietveld refinement |
title_short |
Evolution of oxygen-ion and proton conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), located near pyrochlore fluorite phase boundary |
title_full |
Evolution of oxygen-ion and proton conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), located near pyrochlore fluorite phase boundary |
title_fullStr |
Evolution of oxygen-ion and proton conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), located near pyrochlore fluorite phase boundary |
title_full_unstemmed |
Evolution of oxygen-ion and proton conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), located near pyrochlore fluorite phase boundary |
title_sort |
Evolution of oxygen-ion and proton conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), located near pyrochlore fluorite phase boundary |
author |
Shlyakhtina, A. V. |
author_facet |
Shlyakhtina, A. V. Abrantes, João Gomes, Eduarda Lyskov, N. V. Konysheva, E. Yu. Chernyak, S. A. Kharitonova, E. P. Karyagina, O. K Kolbanev, I. V. Shcherbakova, L. G. |
author_role |
author |
author2 |
Abrantes, João Gomes, Eduarda Lyskov, N. V. Konysheva, E. Yu. Chernyak, S. A. Kharitonova, E. P. Karyagina, O. K Kolbanev, I. V. Shcherbakova, L. G. |
author2_role |
author author author author author author author author author |
dc.contributor.author.fl_str_mv |
Shlyakhtina, A. V. Abrantes, João Gomes, Eduarda Lyskov, N. V. Konysheva, E. Yu. Chernyak, S. A. Kharitonova, E. P. Karyagina, O. K Kolbanev, I. V. Shcherbakova, L. G. |
dc.subject.por.fl_str_mv |
Pyrochlore Pyrochlore–fluorite morphotropic phase region Proton conductivity Oxygen—ion conductivity Grain-boundary conductivity Thermogravimetry Rietveld refinement |
topic |
Pyrochlore Pyrochlore–fluorite morphotropic phase region Proton conductivity Oxygen—ion conductivity Grain-boundary conductivity Thermogravimetry Rietveld refinement |
description |
Sm2-xCaxZr2O7-x/2 (x = 0, 0.05, 0.1) and Gd2-xCaxZr2O7-x/2 (x = 0.05, 0.1) mixed oxides in a pyrochlore-fluorite morphotropic phase region were prepared via the mechanical activation of oxide mixtures, followed by annealing at 1600 °C. The structure of the solid solutions was studied by X-ray diffraction and refined by the Rietveld method, water content was determined by thermogravimetry (TG), their bulk and grain-boundary conductivity was determined by impedance spectroscopy in dry and wet air (100-900 °C), and their total conductivity was measured as a function of oxygen partial pressure in the temperature range: 700-950 °C. The Sm2-xCaxZr2O7-x/2 (x = 0.05, 0.1) pyrochlore solid solutions, lying near the morphotropic phase boundary, have proton conductivity contribution both in the grain bulk and on grain boundaries below 600 °C, and pure oxygen-ion conductivity above 700 °C. The 500 °C proton conductivity contribution of Sm2-xCaxZr2O7-x/2 (x = 0.05, 0.1) is ~ 1 × 10-4 S/cm. The fluorite-like Gd2-xCaxZr2O7-x/2 (x = 0.1) solid solution has oxygen-ion bulk conductivity in entire temperature range studied, whereas proton transport contributes to its grain-boundary conductivity below 700 °C. As a result, of the morphotropic phase transition from pyrochlore Sm2-xCaxZr2O7-x/2 (x = 0.05, 0.1) to fluorite-like Gd2-xCaxZr2O7-x/2 (x = 0.05, 0.1), the bulk proton conductivity disappears and oxygen-ion conductivity decreases. The loss of bulk proton conductivity of Gd2-xCaxZr2O7-x/2 (x = 0.05, 0.1) can be associated with the fluorite structure formation. It is important to note that the degree of Ca substitution in such solid solutions (Ln2-xCax)Zr2O7-σ (Ln = Sm, Gd) is low, x < 0.1. In both series, grain-boundary conductivity usually exceeds bulk conductivity. The high grain-boundary proton conductivity of Ln2-xCaxZr2O7-x/2 (Ln = Sm, Gd; x = 0.1) is attributable to the formation of an intergranular CaZrO3-based cubic perovskite phase doped with Sm or Gd in Zr sublattice. © 2019 by the authors. |
publishDate |
2019 |
dc.date.none.fl_str_mv |
2019-08-01T00:00:00Z 2019-08-01 2022-12-05T11:22:39Z 2023-01-02T15:03:04Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://hdl.handle.net/20.500.11960/3059 |
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http://hdl.handle.net/20.500.11960/3059 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
1996-1944 10.3390/ma12152452 |
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info:eu-repo/semantics/openAccess |
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openAccess |
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application/pdf |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
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